Method for treating hyperglycemia in mammals using arylamino benzoic acids

ABSTRACT

A method for treating hyperglycemia in a mammal which comprises administering internally to said mammal a hypoglycemic amount of an arylamino benzoic acid or pharmaceutically-acceptable salt thereof, wherein aryl represents phenyl, substituted phenyl, thienyl or substituted thienyl.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of copending U.S. PatentApplication Ser. No. 922,002, filed July 3, 1978, now U.S. Pat. No.4,143,151.

BACKGROUND OF THE INVENTION

Diabetes mellitus is a disease of mammals which is characterized by anintolerance to carbohydrates and an inadequate production and secretionof insulin by the β-cells in the islets of Langerhans. The disease isoften associated with vascular degeneration, especially atherosclerosis.Hypoglycemic agents which are effective in lowering blood sugars may beused in the treatment of certain types of diabetes. U.S. Pat. No.3,983,164 describes a group of benzoic acid derivatives which havedemonstrated hypoglycemic activity.

Dutch publication No. 7,602,332 describes various related derivatives ofbenzoic acid which are useful as hypolipidemic agents.

SUMMARY OF THE INVENTION

The present invention relates to a method for lowering blood sugar in amammal which comprises administering internally to the mammal aneffective hypoglycemic amount of a compound having the general formula##STR1## wherein R₁ represents hydrogen or a lower alkyl; R₂ representshydrogen or methyl; n represents an integer of from 0 to 3; and Arrepresents phenyl, thienyl, halo substituted thienyl, or substitutedphenyl wherein the substituted moieties are selected from the groupconsisting essentially of halo, lower alkyl, and trihalomethyl.

As used herein the term lower alkyl refers to an alkyl containing from 1to about 3 carbon atoms, either branched or unbranched. The term loweralkyl thus includes, for example, methyl, ethyl, propyl, and isopropyl.The term halo refers to a halogen substitution selected from the groupconsisting essentially of fluoro, chloro, bromo, and iodo with fluoroand chloro substitutions being particularly preferred.

Pharmaceutically-acceptable salts of the arylaminobenzoic acid compoundsdescribed herein are considered as being within the scope of theinvention. Pharmaceutically-acceptable salts refer to the acid additionsalts of those bases which will form a salt with the carboxylic acid andwhich will not cause an adverse physiological effect when administeredto an animal at dosages consistent with good pharmacological activity.Suitable bases thus include, for example, the alkali metal and alkalineearth metal hydroxides, carbonates, and bicarbonates such as sodiumhydroxide, potassium hydroxide, calcium hydroxide, potassium carbonate,sodium bicarbonate, magnesium carbonate and the like, ammonia, primary,secondary, and tertiary amines and the like. Also aluminum salts of theinstant compounds may be obtained by treating the corresponding sodiumsalt with an appropriate aluminum complex such as, for example, aluminumchloride hexahydrate, and the like.

The arylaminobenzoic acids described above, their esters andpharmaceutically-acceptable salts when used according to the method ofthe present invention show hypoglycemic activity in mammals, i.e. lowerthe level of sugar in the blood. The compounds used in the practice ofthe present invention are therefore particularly suitable for use in thetreatment of diabetes in mammals characterized by abnormally high levelsof sugar in the blood. The compounds can be administered internally tothe mammal either orally or parenterally by subcutaneous, intravenous,or intraperitoneal injection or by implantation or the like. Oraladministration is generally preferred.

The effective hypoglycemic amount of the active compounds to beinternally administered to a mammal, that is the amount which iseffective to significantly lower the amount of sugar in the blood, canvary depending upon such factors as the particular arylaminobenzoicacid, ester, or pharmaceutically-acceptable salt employed, the desiredlevel of blood sugar to be obtained, the severity of the disease, theperiod of administration, and the method of administration. In general,an effective daily dosage range is from about 7 to about 180 milligramsper kilogram of body weight, with a daily dosage range of from about 7to about 60 milligrams per kilograms of body weight being preferred.

DETAILED DESCRIPTION OF THE INVENTION

The compounds used in the practice of the present invention are preparedby condensing a pre-selected aryl aldehyde with p-aminobenzoic acid oran ester thereof. The resulting Schiff base is reduced to prepare thecorresponding free acid. A convenient method of carrying out the latterprocedure involves mixing about 0.1 mol. of the Schiff base with anexcess of ethanol and water. Dilute aqueous sodium hydroxide in anamount of about 0.1 molar equivalent of the Schiff base optionally canbe added to the mixture. Sodium borohydride or other suitable reducingagent (0.1 ml) is added at about room temperature and stirred until itdissolves. The mixture is heated at reflux for about 1 or 2 hours. Theproduct may be separated from the mixture by known procedures andfurther purified if desired.

Pharmaceutically-acceptable salts of the acid may be prepared bytreating the free acid with an appropriate base, that is a base whichwill form a pharmaceutically-acceptable salt with the carboxylic acidand the anions of which are relatively innocuous at dosages consistentwith good pharmacological activity so that the desired hypoglycemicproperties of the salt are not vitiated by side effects ascribable tothe anions.

Examples of compounds prepared using the above method of preparation andhaving hypoglycemic properties are given in the Table below.

In carrying out the method of the present invention, the active compoundcan be administered directly or as an active ingredient of apharmaceutical preparation or composition. To illustrate, for oraladministration, pharmaceutical preparations of the arylaminobenzoicacids may be made by following the conventional techniques of thepharmaceutical chemist. These techniques involve granulating andcompressing the active compound alone or in admixture with othermaterials or variously mixing and dissolving or suspending the activecompound with other ingredients as appropriate to prepare apredetermined end product. Numerous pharmaceutical forms to carry thecompound can be used. For example, the pure compound can be mixed with asolid carrier. Generally, inorganic pharmaceutical carriers arepreferable and particularly solid inorganic carriers. One reason forthis is the large number of inorganic materials which are known to bepharmaceutically safe and acceptable, as well as very convenient inpreparing formulations. The compositions may take the form of tablets,linquets, powders, capsules, troches or lozenges and such compositionsmay be prepared by standard pharmaceutical techniques. Tabletcompositions may be coated or uncoated and they may be effervescent ornon-effervescent. Conventional excipients for tablet formations may beused. For example, inert diluents, such as magnesium carbonate,disintegrating agents such as maize starch or alginic acid, andlubricating agents such as magnesium stearate may be used.

If a liquid carrier is used, the preparation may be in the form of asoft gelatin capsule, a syrup, a liquid solution or a suspension.

The hydrocarbon solubility of the compounds of this invention generallyis sufficiently high to allow the use of pharmaceutically-acceptableoils either as a solvent or as a carrier. For example vegetable oranimal oils such as sunflower oil, safflower oil, maize oil or cod liveroil can be used. Glycerine can also be used. With this latter solvent,for 2 to 30 percent water may be added. When water alone is the carrier,or when the solubility of the compound in the oil is low, thepreparations can be administered in the form of a slurry.

Emulsion compositions may be formulated using emulsifying agents such assorbitan trioleate, polyoxyethylene sorbitan monooleate, lecithin, gumacacia or gum tragacanth. Aqueous based suspensions may be prepared withthe aid of wetting agents such as polyethylene oxide condensationproducts of alkylphenols, fatty alcohols or fatty acids with thesuspending agents, for example a hydrophilic colloid such aspolyvinylpyrrolidone. The emulsions and suspensions may containconventional excipients such as sweetening agents, flowing agents,coloring materials and preservatives.

The arylamino benzoic acids, ester or salt used in the method of thepresent invention also can be incorporated in a nutritive foodstuff suchas, for example, margarine, edible oils, casein, carbohydrates and thelike. Such nutritive compositions are adapted to be administered as apartial or total diet or as a supplement to the diet. Such compositionspreferably contain from about 0.02 or less to about 2.0 or more percentof the active ingredient when administered as the total diet. Thecompositions can contain higher concentrations of the active ingredientwhen administered as a supplement.

For parenteral use, the compounds of this invention can be formulatedwith sterile ingredients, compounded and packaged asceptically. They maybe administered intravenously or intramuscularly. Useful solvents forformulation in such use are the polyhydric aliphatic alcohols andmixtures thereof. Especially satisfactory are thepharmaceutically-acceptable glycols, such as propylene glycol, andmixtures thereof. Glycerine is another example of a polyol which isparticularly useful. Up to 25-30 percent by volume of water may beincorporated in the vehicle if desired. An 80 percent aqueous propyleneglycol solution is a particularly convenient solvent system. A pH range,about 7.4, and isotonicity compatible with body isotonicity, isdesirable. Basicity may be controlled by addition of a base as required,and a particularly convenient base is monoethanolamine. It may often bedesirable to incorporate a local anesthetic and such are well known tothose skilled in the art.

The percentage of the compound to be used in the pharmaceutical carriermay be varied. It is necessary that the compound constitute a proportionsuch that a suitable dosage will be obtained and it is preferred to usepharmaceutical compositions containing at least 10 weight percent of thecompound. Activity increases with concentration of the agent in thecarrier, but those compositions containing a significant amount ofcarrier, e.g. at least 1 percent and preferably at least 5 percent, arepreferred as they allow for the easier administration of the compound.

The hypoglycemic activity of the subject compounds was demonstrated inalanine-induced hypoglycemic mice. Alanine is the most glucogenic of theamino acids and also stimulates gluconeogensis in normal animals.Animals suffering from diabetes show an exaggerated hyperglycemicresponse to a protein or amino acid meal, therefore the hyperglycemicstate induced by alanine closely parallels the response of a diabeticmammal.

Studies demonstrating the hypoglycemic activity of the subject compoundswere carried out by interpertioneally injecting fasted maleSwiss-Webster mice with 60 mg/kg of body weight of the active compound.Fifteen minutes later the same mice were injected intrapertioneally with10 m moles/kg body weight of L-alanine. Sixty minutes after injection ofthe active compound, the animals were sacrificed and their sera wereanalyzed for glucose. The control consisted of both fasted mice and miceinjected with alanine. The results are expressed as percent lowering ofserum glucose from the alanine induced hyperglycemic level to the fastedcontrol glucose level, i.e. lowering to the fasting glucose level is100% lowering.

The results obtained using the method described above is given in thefollowing Table.

                                      TABLE                                       __________________________________________________________________________    Example                           % Lowering                                  No.  Compound Name                Blood Sugar*                                __________________________________________________________________________    1    p-anilinobenzoic acid        88                                          2    4-(((4-(1-methylethyl)phenyl)methyl)amino)benzoic acid                                                     78                                          3    4-(((4-chlorophenyl)methyl)amino)benzoic acid                                                              111                                         4    4-(((4-methylphenyl)methyl)amino)benzoic acid                                                              144                                         5    4-(((4-ethylphenyl)methyl)amino)benzoic acid                                                               96                                          6    4-(((4-fluorophenyl)methyl)amino)benzoic acid                                                              110                                         7    4-((2-thienylmethyl)amino)benzoic acid ethyl ester                                                         78                                          8    4-((2-thienylmethyl)amino)benzoic acid                                                                     51                                          9    4-(((3-chlorophenyl)methyl)amino)benzoic acid                                                              64                                          10   4-((3-phenylpropyl)amino)benzoic acid                                                                      99                                          11   4-(((4-(trifluoromethyl)phenyl)methyl)amino)benzoic                                                        106d                                        12   4-(((4-chlorophenyl)methyl)amino)benzoic acid sodium                                                       129t                                        13   4-(((3-fluorophenyl)methyl)amino)benzoic acid                                                              52                                          14   4-(((4,5-dichloro-2-thienyl)methyl)amino)benzoic acid                                                      83                                          15   4-(((5-bromo-2-thienyl)methyl)amino)benzoic acid                                                           210                                         __________________________________________________________________________     *as compared to control group.                                           

The results demonstrate the hypoglycemic activity of representativecompounds falling within the scope of the present invention. Thosecompounds wherein the substitution is halo or lower alkyl are preferredas are those compounds wherein Ar represents substituted phenyl.

The effective dose (ED₅₀) of several of the subject compounds weredetermined. The following compounds showed the lowest ED₅₀ 's of thecompounds actually tested and therefore represent preferred embodimentsof the invention.

    ______________________________________                                        Compound         ED.sub.50 * in mg/kg                                         Example No.      body weight                                                  ______________________________________                                        3                11                                                           4                15                                                           5                15                                                           12               6                                                            15               4.6                                                          ______________________________________                                         *effective dose represents the amount of the active ingredient required t     obtain a 50% reduction in serum glucose as compared to the control            animals.                                                                 

The compound 4-(((5-bromo-2-thienyl)methylamino)benzoic acid (Example15) showed the highest activity as a hypoglycemic agent of the compoundstested, and represents the preferred embodiment of the presentinvention. This compound continued to show significant hypoglycemicactivity in mice at dosages as low as 7.5 mg per kg of body weight.

What is claimed is:
 1. A method for treating hyperglycemia in a mammalwhich comprises administering internally to said mammal an effectivehypoglycemic amount of the compound4-(((5-bromo-2-thienyl)methyl)amino)benzoic acid orpharmaceutically-acceptable salt thereof.